The oldest profession in the world, legalized through the power of SwapDollars. Well, okay, in places like Australia it's already legal. But if we can get the workers of the demimonde to credit SwapDollars worldwide we'll have a network bigger than Mastercard in no time. Um, no pun intended ...
One of the nice things about the fact that SwapDollars are not a monetary unit is that no one has to credit them. A SwapStitution racket is no different to any dating agency - it's just got a certain guarantee of service quality attached ...
Then marriage is subset of steady-state SwapStitution!